type OnlyOptional<S extends string> =
  S extends `${infer K}}?` ? K
  : S extends `${infer K}?` ? K
  : never;
type OnlyRequired<S extends string> = S extends `${string}?` ? never : S;

/** Parameters for a given path */
export type PathArgs<S extends string> =
  PathKeys<S> extends never ?
    // unknown is identity for intersection ('&')
    unknown
  : KeysToArgs<PathKeys<S>>;

/** Computes the union of keys for a path string */
export type PathKeys<S extends string> =
  string extends S ? string
  : S extends `${infer A}\\${':' | '?' | '+' | '*' | '{' | '}'}${infer B}` ?
    PathKeys<A> | PathKeys<B>
  : PathSplits<S>;

type PathSplits<S extends string> =
  S extends (
    `${string}:${infer K}${'/' | ',' | '%' | '&' | '+' | '*' | '{'}${infer R}`
  ) ?
    PathSplits<`:${K}`> | PathSplits<R>
  : S extends `${string}:${infer K}:${infer R}` ?
    PathSplits<`:${K}`> | PathSplits<`:${R}`>
  : S extends `${string}:${infer K}` ? K
  : never;

export type KeysToArgs<Key extends string> = {
  [K in Key as OnlyOptional<K>]?: string | number;
} & (OnlyRequired<Key> extends never ? unknown
: {
    [K in Key as OnlyRequired<K>]: string | number;
  });

export type PathArgsAndSearch<S extends string> =
  OnlyRequired<PathKeys<S>> extends never ?
    Record<string, number | string | boolean> | undefined
  : {
      [K in PathKeys<S> as OnlyRequired<K>]: string | number;
    } & Record<string, number | string>;

/** Removes the last :token */
export type ShortenPath<S extends string> =
  string extends S ? string
  : S extends `${infer B}:${infer R}` ? TrimColon<`${B}:${ShortenPath<R>}`>
  : '';

type TrimColon<S extends string> =
  string extends S ? string
  : S extends `${infer R}:` ? R
  : S;

export type ResourcePath = string; // `${string}:${string}`; TODO: Maybe do this in the future? Seems to hard to understand for now